1. Technical Field
The present invention relates to an apparatus for reducing backlash in a gear wheel, which wheel comprises (includes, but is not limited to) at least two interacting gear rims that can rotate in relation to one another, and at least one adjusting means located between the gear rims for adjusting the relative angle of rotation of the gear rims about a common axis of rotation.
2. Background Art
In internal combustion engines with an overhead camshaft, use is sometimes made of a gear train for driving the camshaft. In this connection, the gear train can comprise three or more serially arranged gear wheels. As the camshaft controls the opening and closing of spring-operated valves, the camshaft is acted on by greatly varying torques during its rotation. This means that any backlash which arises in the tooth engagement normally gives rise to a high level of noise and also tooth wear.
In order to restrict backlash to a minimum, as many gear wheels as possible are mounted in the same part, for example in a common transmission plate. In engines with an overhead camshaft, however, the camshaft wheel is, of necessity, mounted in another part, the tolerance chain then being longer and the precision poorer. Although the position of, for example, an intermediate wheel can be designed so as to be adjustable, the backlash can nevertheless be unacceptably great.
An apparatus is known from U.S. Pat. No. 5,979,260, the disclosure of which is herein expressly incorporated by reference, which is intended to reduce the backlash in a gear train. This apparatus comprises a gear wheel with gear rims which are divided in the wheel plane and can be displaced in terms of rotation so that the projecting and resulting tooth width increases and fills the tooth gap. The gear wheel is equipped with powerful springs which hold the two tooth flanks apart so that the backlash is zero in at least one tooth engagement. As space is normally very limited and great forces are required, this is a very difficult construction in which, on the one hand, to find room for sufficiently strong springs, and on the other hand, because these are very rigid and tolerance-sensitive, to get all the springs to work reasonably alike and to achieve the desired precision of the forces.